The ones in orange lights that have messages like "Look out for bikes", "Keep your distance" or "Don't drink and drive"
To me, it seems that there more likely to be a distraction than to actually change anyone's behaviour. I mean, if you're the kind of driver who doesn't routinely keep your distance, is that going to change because a sign tells you to?
Meanwhile, the majority of drivers, who do routinely follow this advice are distracted momentarily while they read the signs.